Hi,
I have seen in tinyos-2.x you compute the lqi as:
CC2420ReceiveP.nc:
metadata->crc = buf[ length ] >> 7;
metadata->rssi = buf[ length - 1 ];
metadata->lqi = buf[ length ] & 0x7f;
CC2420PacketC.nc:
async command error_t CC2420Packet.getLqi( message_t* p_msg ) {
return getMetadata( p_msg )->lqi;
}
However,in the cc2420 datasheet says that this is the correlation
value of the 8 first symbols following the SFD, which ranges [50,110],
and it represents somehow a "chip error rate". LQI value must be later
calculated by software to convert this value to a range of 0-255
(either using a combination of RSSI and corr or using PER measurements).
So, what I understand is that this value from tinyos is the correlated
value of this 8 symbols instead of the LQI of 802.15.4. Is that right?
And what this correlated value is exactly? My understanding is that is
a correlation between the chip that is suposed to be received in the
receiver and the chip received (signal + noise). Does that make sense
for you?
Regards,
----
Rodo
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